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Description:Color Doppler suggests disturbed flow patterns in the area of luminal narrowing.

Caption:Spectral waveform analysis of the proximal Rt. ICA

Description:The proximal part of the right ICA shows a normal arterial waveform with normal peak systolic and end diastolic velocities.

Caption:Spectral waveform analysis of the Rt. ICA-mid part

Description:An abnormal waveform is noted with spectral broadening and elevated peak systolic and end diastolic velocities.

Caption:Spectral waveform analysis of the distal Rt. ICA

Description:The abnormally elevated velocities still persist in the distal portion of the right ICA.

Caption:Sagittal image of the left carotid bulb and ICA

Description:The left carotid bulb and the origin of the ICA appear normal. The distal part of the ICA shows a relatively long segment of narrowing.

Caption:Color Doppler image of the left ICA

Description:The color Doppler image shows the segment of stenosis. A few small outpouchings are also noted in the distal part of the ICA.

Caption:Spectral waveform analysis of the proximal Lt. ICA

Description:The proximal part of the left ICA shows a normal arterial waveform with normal peak systolic and end diastolic velocities.

Caption:Spectral waveform analysis of the Lt. ICA-mid part

Description:A normal arterial waveform is recorded.

Caption:Spectral waveform analysis of the distal Lt. ICA

Description:An abnormal waveform is noted with elevated peak systolic and end diastolic velocities.

Differential Diagnosis

Bilateral fibromuscular dysplasia of the carotid artery.

Final Diagnosis

Bilateral fibromuscular dysplasia of the carotid artery.

Discussion

Fibromuscular dysplasia [FMD] of the carotid artery is a non-atheromatous angiopathy that mostly affects middle aged woman. It affects the medium and large arteries, the most common being renal followed by carotid. This disease was first described in 1938 by Leadbetter and Burkland.

This disease is bilateral in about 75% of the patients. Its etiology is unknown. The arteries other than renal and carotid to be involved are vertebral, lumbar, mesenteric, celiac, hepatic and iliac arteries. A deficiency of alpha-1 antitrypsin, mechanical trauma, genetic predisposition, ischemia of arterial wall and /or immunologic factors have been implicated in its pathogenesis.

Types- Four histological types of FMD have been described:1. Intimal fibroplasia 2. Medial hyperplasia3. Perimedial dysplasia and 4. Medial fibroplasia – this is the commonest and occurs in 90% cases. It produces multiple areas of arterial stenosis.

FMD is known to have an association with intracranial aneurysms, spontaneous dissections in the affected vessels, carotico-cavernous fistulas, thrombo-embolism and hemodynamic compromise of the distal circulation.

Angiography is the preferred imaging modality; however ultrasound, CT angio or MR angio may be the initial imaging modality.

Ultrasound features: According to the criteria by Arnig, etc. ultrasound criteria of FMD correspond to those of angiography and include-• Segmental String of Beads pattern with alternating areas of luminal narrowing and dilatation. • Localization in the distal part of internal carotid artery or vertebral artery.• Direct and/or indirect criteria of stenosis which may be unifocal or multifocal.A pattern that is noted in atypical fibromuscular dysplasia is involvement of only one wall of the affected segment which may show a diverticulum-like smooth outpouching.

Differential diagnosis:1. Takayasu’s arteritis – this is an inflammatory angiopathy that involves the aorta and other major branches of the aorta. Stenosis is much more commonly seen than aneurysms.

Management- If the patient has symptomatic carotid artery disease, surgery in the form of arterial resection and graft placement or percutaneous transluminal angioplasty with or without stenting may be performed. If the FMD is asymptomatic it can be managed conservatively.

A CT angiography was performed which confirmed the diagnosis of bilateral fibromuscular dysplasia affecting the carotid artery without significant luminal stenoses. Imaging of major abdominal vessels revealed no abnormality. The patient was offered regular surveillance.